Process and apparatus for rejoining a thread on an open-end friction-spinning device

Abstract

A process for rejoining the thread on an open-end friction-spinning device, in which fibers are fed into a V-shaped nip subjected to suction, and the thread formed in the V-shaped nip is drawn off from this and wound onto a bobbin. For rejoining, the fiber feed into the V-shaped nip is interrupted and a thread end drawn off from the bobbin is guided towards the V-shaped nip counter to the spinning direction. This thread end is paid out in front of the V-shaped nip and is stored in a joinable length in a storage station at the end of the V-shaped nip facing away from the bobbin. The bobbin is then advanced towards its drive roller and the thread is drawn off from the storage station. After a predetermined time after the start of the thread draw-off, the fibers are fed again into the V-shaped nip, where they come up against the thread end running through the V-shaped nip and are twisted together with this.

We claim: 
     
       1. A process for rejoining a thread for restarting the spinning process on an open-end friction-spinning device, in which fibers are fed into a V-shaped nip formed by two driven friction rollers and subjected to suction, and the thread formed in the V-shaped nip is drawn off from the nip and wound onto a bobbin driven by drive roller, comprising the steps of: providing a joinable length of a thread end for the V-shaped nip;   storing a predetermined length of said thread at the end of the V-shaped nip opposite the bobbin;   starting the thread draw off in coordination with the friction roller speed;   twisting said thread; and   starting the fiber feed into the V-shaped nip formed by said driven friction rollers when a predetermined length of thread remains in said storage, whereby a smooth uniform length joint is formed between the thread being formed by the friction rollers and the thread end which had been stored.   
     
     
       2. A process as claimed in claim 1, wherein the thread end is laid out in front of a vertically extending V-shaped nip formed by said driven friction rollers. 
     
     
       3. A process as claimed in claim 1 or 2, wherein the thread end is stored in a pneumatic storage station. 
     
     
       4. A process as claimed in claim 3, wherein the suction exerted on the V-shaped nip is interrupted before the laying-out operation. 
     
     
       5. A process as claimed in claim 4, wherein the friction elements are cleaned before the laying out of the thread end by being driven in the opposite direction to the direction of rotation for spinning, the residual fibers coming loose from them being sucked into the storage station. 
     
     
       6. A process as claimed in claim 5, wherein a metered thread length is stored in the storage station. 
     
     
       7. A process as claimed in claim 5, wherein a thread length exceeding a predetermined joining length is stored in the storage station, and the absolute thread end is sensed during the thread draw-off. 
     
     
       8. A process as claimed in claim 7, wherein the thread end laid out in front of the V-shaped nip is held elastically at a distance from the thread transfer device. 
     
     
       9. A process as claimed in claim 8, wherein the thread end drawn off from the bobbin is guided laterally past a pair of draw-off rollers and is held elastically at a distance from the nip line of the pair of draw-off rollers. 
     
     
       10. A process as claimed in claim 9, wherein the thread end is prepared for joining before the laying-out operation. 
     
     
       11. An apparatus for rejoining a thread for restarting the spinning process on an open-end friction spinning device, said spinning device comprising: two rotationally symmetrical friction elements supported on a frame to form a V-shaped nip, at least one of which is perforated and is connected to a suction device by a suction tube;   a fiber feeding device having a sliver supply and an opening device;   a pair of draw off rollers;   a spooling device;   a thread monitor arranged between said draw off rollers and said spooling device;   a lift off device for lifting the bobbin off its drive means;   a sliver clamping device disposed adjacent to the sliver supply device; and   a thread storage device arranged in front of the friction element in a position to retrieve and to store broken ends of thread.   
     
     
       12. An apparatus as claimed in claim 11 wherein the thread storing means comprises a suction tube and a shutoff valve. 
     
     
       13. An apparatus as claimed in claim 12 which further comprises control means for activating the bobbin lift off device, to close the sliver clamping device, to open the shut off valve of the thread storing means, and to close the shut off valve of the suction device for the frictional elements whenever the thread monitor detects a broken thread. 
     
     
       14. An apparatus as claimed in claim 12 which comprises a control means for activating the bobbin lift off device to re-engage the bobbin with its drive roller, the sliver clamping device to release the sliver; opening the shutoff valve of the suction tube for the friction elements; and   for closing the shut off valve of the thread storage in accordance with a predetermined, time controlled program.   
     
     
       15. An apparatus as claimed in claim 14, wherein the control is carried out by means of a microprocessor 
     
     
       16. An apparatus as claimed in claim 15, wherein a thread sensing device is assigned to the thread store. 
     
     
       17. An apparatus as claimed in claim 16, wherein the thread sensing device is a light barrier. 
     
     
       18. An apparatus as claimed in claim 12, wherein the thread storage device is at the same time a suction device for removing loose fiber from the friction elements. 
     
     
       19. An apparatus as claimed in claim 18, wherein an elastic thread guide element is arranged in front of the thread transfer device belonging to the spooling device. 
     
     
       20. An apparatus as claimed in claim 19, wherein the pair of draw-off rollers has assigned to it an elastic thread guide element which holds the thread at a distance from it. 
     
     
       21. An apparatus as claimed in claim 20, wherein the friction elements are arranged vertically upright. 
     
     
       22. An apparatus as claimed in claim 21, wherein the thread store is arranged in a servicing trolley movable along the spinning units. 
     
     
       23. An apparatus as claimed in claim 22, wherein the thread store has a suction nozzle which can be moved out of an initial position and which is intended for paying-out the thread. 
     
     
       24. An apparatus as claimed in claim 23, wherein the suction nozzle can be moved relative to the bobbin in order to search for and suck up the broken thread end. 
     
     
       25. An apparatus for rejoining a thread, especially as claimed in claim 24, wherein a device for preparing the free thread end is arranged in the thread store. 
     
     
       26. An apparatus as claimed in claim 25, wherein the suction nozzle is part of the thread store and is fastened to a gripper, by which it can be moved out of an initial position into a thread search position, back to the initial position for paying-out the thread in front of the V-shaped nip and out of the initial position into a position for inserting the thread into the V-shaped nip. 
     
     
       27. A process for rejoining a thread on an open-end friction-spinning device, in which fibers are fed into a V-shaped nip subjected to suction, and the thread formed in the V-shaped nip is drawn off from said V-shaped nip and wound onto a bobbin, and, for rejoining, a thread end is drawn off from the bobbin and guided towards the V-shaped nip, wherein the thread drawn off from the bobbin is first laid out in front of the V-shaped nip and is stored in a predetermined length in a storage station, and wherein the thread is then inserted into the V-shaped nip from this position, whereupon, after a predetermined time, the fiber feed into the V-shaped nip is resumed. 
     
     
       28. A process as claimed in claim 27, wherein the thread draw-off from the storage station takes place together with the start of the movement of the thread from the paying-out position into the V-shaped nip. 
     
     
       29. A process as claimed in claim 27 or 28, wherein the suction exerted on the V-shaped nip is maintained during the entire paying-out operation. 
     
     
       30. A process as claimed in claim 1, wherein the fiber feeding is started a predetermined time after the thread draw off is started.